This invention is an evolution of previous inventions by the same inventor, Charles A. Walton, as follows:
1. U.S. Pat. No. 4,223,830, titled "Identification System" and issued on Sept. 23, 1980;
2. U.S. Pat. No. 4,236,068, titled "Personal Identification and Signalling System", and issued on Nov. 25, 1980;
3. U.S. patent application Ser. No. 221,720, "Portable Radio Frequency Emitting Identifier", filed on Dec. 31, 1980; now U.S. Pat. No. 4,384,288.
4. U.S. patent application Ser. No. 06/264,856, "Identification System with Separation and Direction Capability and Improved Noise Rejection", filed on May 18, 1981; and
5. U.S. patent application Ser. No. 302,706, "Electronic Identification and Recognition with Code Changeable Reactance", filed on Sept. 16, 1981; now U.S. Pat. No. 4,388,524.
The above patents and patent applications are incorporated by reference in the subject application.
In application Ser. No. 302,706, it is shown that the antenna of an identifier can be used to both receive power from the reader station and radiate power to the reader, in one case at differing time intervals. It is also shown that the data can be sent on several differing radio frequencies, and the power be received on another radio frequency. Application Ser. No. 264,856 also shows data being transmitted from an identifier to the reader on several different radio frequencies.
Several problems arise with dual use of the identifier antenna for both receiving power and sending data. One is that while radiating information from the antenna of the identifier, the power-receive circuits are also connected to the antenna and may absorb useful energy from the sending circuit. Conversely, while the identifier is receiving power, the power radiation circuits may absorb useful energy and make the power reception function less efficient. A second problem is that messages from the identifier must be optimally synchronized with the power pulses from the reader. It is one of the objectives of the present invention to show how this dual use of the identifier antenna may be achieved, without harmful effects.
In application Ser. No. 264,856 and U.S. Pat. No. 4,236,068, a system is described in which two or more radio frequencies are used in an identifier, with the advantage that noise can be better rejected, and in which when four frequencies are used, then a doubling of the code bits is achieved within the same transmission time. This doubling occurs because each frequency can represent two bits, or four different values, rather than one bit for two values.
In patent application Ser. No. 264,856, is also described how fraud can be reduced if, within the card memory, there is recorded a description of the authorized bearer of the authorized bearer of the card, and this description is made readily available to a merchant processing a transaction. With this description the merchant may quickly check the appropriateness of the bearer. It is a further object of this invention to show that the same technique can be extended to include vehicle identification, so that within the memory of the card there is at least the license plate number of the automobile of the authorized bearer of the card. A gasoline station attendant selling gasoline is given a display of the card contents showing the recorded license number and can quickly verify that the card is being presented to purchase fuel for an authorized vehicle.
It is a further object of this invention to show that the data on the description of the authorized bearer may come from storage in the card and also from storage in the central recording point or from storage at the reading station.
It is a further object of this invention to show how the encoding function can be achieved with a matrix of diodes, any of which can selectively be "blown" or destroyed to create the desired code specific to the bearer and which includes the identification of the authorized bearer.